Effect of Laser Beam Oscillation Process on the Interlaminar Region of Inconel 625 Alloy Thin-Walled Structure Fabricated by Oscillating Laser Additive Manufacturing

In the multilayer thin-walled Inconel 625 alloy structures fabricated by the laser additive manufacturing (LAM) process, the poor plasticity of the interlaminar region often leads to structural fractures. In this paper, an oscillating LAM (O-LAM) technology using a transverse linear beam oscillation (LBO) process was proposed, and the effect of laser scanning speed on the forming accuracy, microstructure, crystallographic texture, and mechanical properties of interlaminar region was studied. The results show that the LBO process refined the grains and increased the number and length of high-angle grain boundaries in the interlaminar region. In addition, the LBO process with high laser scanning speed weakened the preferential orientation along the directions of laser scanning and deposition build-up. In particular, the dominant crystallographic textures of {110} <111> and {221} <110> in the interlaminar region were significantly reduced. The analysis of the Schmidt factor and the results of nano-indentation test show that the LBO process with high laser scanning speed reduced the stress concentration, and the elastic modulus and dislocation density in the interlaminar region. Therefore, the LBO process with high laser scanning speed can improve the plasticity and relieve the stress concentration of the interlaminar region, which is conducive to improving the overall mechanical properties of the Inconel 625 alloy multilayer thin-walled structure.